
import {
	Blob,
	btoa,
	createImageBitmap,
	CSSStyleDeclaration,
	performance,
	document,
	DOMParser,
	EventTarget,
	fetch,
	Headers,
	HTMLCanvasElement,
	Image,
	HTMLImageElement,
	ImageBitmap,
	location,
	navigator,
	Request,
	requestAnimationFrame,
	cancelAnimationFrame,
	Response,
	URL,
	window,
	self,
	WebAssembly,
	Worker,
	XMLHttpRequest,
	ImageData,
	TextDecoder,
	core
	} from 'dhtml-weixin';
import { div } from '../../math/OperatorNode.js';
import { EPSILON } from '../../math/MathNode.js';
import { tslFn } from '../../shadernode/ShaderNode.js';

// Moving Frostbite to Physically Based Rendering 3.0 - page 12, listing 2
// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
const V_GGX_SmithCorrelated = tslFn( ( inputs ) => {

	const { alpha, dotNL, dotNV } = inputs;

	const a2 = alpha.pow2();

	const gv = dotNL.mul( a2.add( a2.oneMinus().mul( dotNV.pow2() ) ).sqrt() );
	const gl = dotNV.mul( a2.add( a2.oneMinus().mul( dotNL.pow2() ) ).sqrt() );

	return div( 0.5, gv.add( gl ).max( EPSILON ) );

} ).setLayout( {
	name: 'V_GGX_SmithCorrelated',
	type: 'float',
	inputs: [
		{ name: 'alpha', type: 'float' },
		{ name: 'dotNL', type: 'float' },
		{ name: 'dotNV', type: 'float' }
	]
} ); // validated

export default V_GGX_SmithCorrelated;
